Sliver cans are known for receiving and dispensing sliver in connection with textile machines processing sliver. These textile machines typically include a plurality of spinning or work stations and a sliver can located at each spinning station. In operation, sliver is drawn from each sliver can into the spinning station and fed into a spinning unit. If a can containing sliver becomes empty at a work station of a textile machine processing slivers, the empty can is typically exchanged for a full can. While the empty can is being exchanged, there is a break in the production which results in a reduction of productivity. To minimize the downtimes of the textile machines, it is known to monitor the fill state of the sliver cans, so that when a sliver can becomes empty, the exchange of the empty can for a full can may be initiated. For example, it is known from German Patent Publication DE 36 14 654 A1, to utilize a sensor at the piecing carriage of a textile machine to monitor the fill state of the sliver cans at the individual spinning stations of an open-end spinning machine. The sensor is positioned on the underside of the piecing carriage and monitors the fill state of each sliver can in the course of the travel of the piecing carriage along the spinning machine, and reports the location of a completely empty sliver can to a control device on the machine, which then initiates the exchange of the empty can for a freshly filled one, or the filling of the empty can. One disadvantage of this method is that an indefinite period of time passes before an empty can is sensed by the sensor on the piecing carriage and the exchange or filling, of the can is initiated.
Different methods for monitoring the degree of filling of sliver cans are described in German Published, Non-Examined Patent Application DE-OS 25 54 915. In one method, an ultrasound transmitter/receiver unit, for example, is proposed for monitoring the fill level of the sliver. In this method, the monitoring stations are provided at each work station. When the fill level of each sliver can falls below a defined preset threshold value, the sliver can is exchanged. Although this method eliminates the time period between when a sliver can is emptied and when the sliver can is exchanged for a full can, a disadvantage is that the sliver can is exchanged while more than an inconsiderable amount of sliver remains in each sliver can. Thus, because the sliver can is exchanged before the sliver is depleted from the can, the amount of sliver which can be drawn from the can before it is exchanged is less than the full capacity of the can and the can is not fully utilized. Therefore, this method undesirably increases the number of times the sliver cans must be exchanged. In addition, this method requires the removal of the sliver remaining in each can after such can has been exchanged for a full sliver can.